The present invention relates to a side printing apparatus for applying latent images of information marks such as manufacturer's name, film type, frame number, date information, production lot number and the like described in characters, numerals, symbols and the like onto the margins of a photographic film during the manufacture thereof and, more particularly, to such apparatus which is adapted to change the exposure of film to a light image produced by a light image forming arrangement installed therein.
In the manufacture of photographic film, it is usual to apply latent images of information marks such as manufacturer's name, frame number and the like along the longitudinal margin or margins of a film. The procedure of applying latent images on a film is generally called as side printing and is performed by side printing apparatus. There have been generally known and widely used various types of side printing apparatus as disclosed in Japanese Utility Model Publication No. 16589/'81, Japanese Pat. unexamined Publication Nos. 42037/'82 and 163226/'82 and Japanese Utility Model unexamined Publication 38341/'81. Such apparatus may be generally divided into four types in accordance with the form of light image forming arrangement. One is a projection arrangement in which a pattern plate and a light source such as lamp, light emitting diode or the like for illuminating the pattern plate are used to project images of information marks onto a film, another is a light emitting diode (LED) matrix array in which a plurality of LEDs are selectively driven to form light marks, the third is a information mark display device such as cathode ray tube, and the last is a two-dimentional laser beam scanning device for successibly scanning a film with a laser spot. For the purpose of applying latent images on a film without incurring any adverse blurring effects, the light image forming device is adapted to move in synchronism with the motion of film or otherwise to be energized for a very short interval.
For adapting a side printing apparatus to various kinds of film with different sensitivity, a requirment for the side printing apparatus is that the exposure of film to light images is adaptable in accordance with the sensitivity of a film to provide the film with a preferred density of images of information marks. In conventional side printing apparatus, the adjustment of exposure is caused as a result of change of the intensity of current through the light image forming device which is done by manipulating a manually operable dial.
One of the problems associated with the side printing apparatus above-mentioned is concerned with inexpediency characterized by bother of the manupulation of the dial to adjust the exposure which results in waste of time.